Question

尝试设置cap_setgid，cap_setuid，cap_setpcap。

#include <sys/types.h>
#include <sys/capability.h>

int main()
{
    cap_t caps;
    caps = cap_get_proc();
    cap_value_t cap_list[2];

    cap_list[0] = CAP_SETUID;
    cap_list[1] = CAP_SETGID;

    cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_list, CAP_SET);
    cap_set_flag(caps, CAP_INHERITABLE, 2, cap_list, CAP_SET);
    cap_set_proc(caps);
    cap_free(caps);
    setgid(65534);
    setuid(65534);

    cap_get_proc();
    setgid(0);
    setuid(0);

    return 0;
}

执行是在root用户下进行的。跟踪程序显示此

capget({_LINUX_CAPABILITY_VERSION_3, 0}, NULL) = 0
capget({_LINUX_CAPABILITY_VERSION_3, 0}, {CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, 0}) = 0
capset({_LINUX_CAPABILITY_VERSION_3, 0}, {CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, CAP_SETGID|CAP_SETUID|CAP_SETPCAP}) = 0
setgid(65534)                           = 0
setuid(65534)                           = 0
capget({_LINUX_CAPABILITY_VERSION_3, 0}, NULL) = 0
capget({_LINUX_CAPABILITY_VERSION_3, 0}, {0, 0, CAP_SETGID|CAP_SETUID|CAP_SETPCAP}) = 0
setgid(0)                               = -1 EPERM (Operation not permitted)
setuid(0)                               = -1 EPERM (Operation not permitted)
exit_group(0)                           = ?
+++ exited with 0 +++

权限已设置但不起作用。有什么建议如何解决这个问题？

更新：prctl已添加到代码

21a22
> prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
24a26
> cap_set_flag(caps, CAP_EFFECTIVE, 3, cap_list, CAP_SET);

所以现在是

prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
setgid(65534);
setuid(65534);
cap_set_flag(caps, CAP_EFFECTIVE, 3, cap_list, CAP_SET);

在setuid之后继承了上限，并且手动设置的上限仍在那里，但它没有解决问题

setgid(65534)                           = 0
setuid(65534)                           = 0
capget({_LINUX_CAPABILITY_VERSION_3, 0}, NULL) = 0
capget({_LINUX_CAPABILITY_VERSION_3, 0}, {0, CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, CAP_SETGID|CAP_SETUID|CAP_SETPCAP}) = 0
setgid(0)                               = -1 EPERM (Operation not permitted)
setuid(0)                               = -1 EPERM (Operation not permitted)
exit_group(0)                           = ?
+++ exited with 0 +++

UPDATE2：无法理解。我在第一setuid之后添加了2个，以查看大写字母。

printf("cape set %d\n", cap_set_flag(caps, CAP_EFFECTIVE, 3, cap_list, CAP_SET));
printf("%s\n", cap_to_text(cap_get_proc(), NULL));

它返回了

catp set 0
=p cap_setgid,cap_setuid,cap_setpcap+i

未设置有效标志，但cap_set_flag返回0

Answer 1

默认情况下，功能集在UID转换中丢失;使用

prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);

保留允许的功能（cap_set_flag(caps, CAP_PERMITTED, ...)）。请注意，有效功能集将被重置，但可以重新建立。

以下对我来说很好。

#include <sys/capability.h>
#include <sys/prctl.h>
#include <unistd.h>

int main(int argc, char **argv) {
    cap_value_t cap_values[] = {CAP_SETUID, CAP_SETGID};
    cap_t caps;

    caps = cap_get_proc();
    cap_set_flag(caps, CAP_PERMITTED, 2, cap_values, CAP_SET);
    cap_set_proc(caps);
    prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
    cap_free(caps);

    setgid(65534);
    setuid(65534);

    caps = cap_get_proc();
    cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET);
    cap_set_proc(caps);
    cap_free(caps);

    setgid(0);
    setuid(0);

    return 0;
}

$ sudo strace ./a.out
...
capget({_LINUX_CAPABILITY_VERSION_3, 0}, {CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, 0}) = 0
capset({_LINUX_CAPABILITY_VERSION_3, 0}, {CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, 0}) = 0
prctl(PR_SET_KEEPCAPS, 1)               = 0
setgid(65534)                           = 0
setuid(65534)                           = 0
capget({_LINUX_CAPABILITY_VERSION_3, 0}, NULL) = 0
capget({_LINUX_CAPABILITY_VERSION_3, 0}, {0, CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, 0}) = 0
capset({_LINUX_CAPABILITY_VERSION_3, 0}, {CAP_SETGID|CAP_SETUID, CAP_CHOWN|CAP_DAC_OVERRIDE|CAP_DAC_READ_SEARCH|CAP_FOWNER|CAP_FSETID|CAP_KILL|CAP_SETGID|CAP_SETUID|CAP_SETPCAP|CAP_LINUX_IMMUTABLE|CAP_NET_BIND_SERVICE|CAP_NET_BROADCAST|CAP_NET_ADMIN|CAP_NET_RAW|CAP_IPC_LOCK|CAP_IPC_OWNER|CAP_SYS_MODULE|CAP_SYS_RAWIO|CAP_SYS_CHROOT|CAP_SYS_PTRACE|CAP_SYS_PACCT|CAP_SYS_ADMIN|CAP_SYS_BOOT|CAP_SYS_NICE|CAP_SYS_RESOURCE|CAP_SYS_TIME|CAP_SYS_TTY_CONFIG|CAP_MKNOD|CAP_LEASE|CAP_AUDIT_WRITE|CAP_AUDIT_CONTROL|CAP_SETFCAP, 0}) = 0
setgid(0)                               = 0
setuid(0)                               = 0
...

Answer 2

我认为您将CAP_PERMITTED集与CAP_INHERITABLE混淆了，除非使用thread / exec，否则要使用CAP_PERMITTED。

可继承（以前称为允许）：将此设置与线程的可继承集进行“与”操作，以确定在线程中启用了哪些可继承功能。 execve（2）之后的允许的线程集

对于update2：尝试在打印之前/之后打印cap_to_text(cap_get_proc())，并考虑cap_set_flag和cap_set_proc之间的区别。

setuid（）之后失去能力

2 个答案: